Hyperglycemia-induced oxidative stress affects multiple signal transduction and metabolic pathways. One of them is poly(ADP-ribosyl)ation induced by hydroxyl and superoxide radicals and peroxynitrite- stimulated DNA single-strand breakage. The OVERALL HYPOTHESIS of this proposal is that activation of endothelial and Schwann cell poly(ADP-ribose)synthetase (PARS), associated with NAD depletion, energy failure and, potentially, exacerbation of oxidative stress, contributes to neurovascular dysfunction, nerve conduction deficits, impaired neurotrophic support and morphological changes of peripheral diabetic neuropathy (PDN). The RATIONALE is based on the: 1) key role of oxidative stress in nerve blood flow (NBF), conduction and nerve growth factor (NGF) deficits of PDN; 2) key role of poly(ADP-ribosyl)ation in free radical damage in numerous pathologies (e.g. cardiovascular and neurodegenerative diseases, inflammation) associated with oxidative stress; 3) presence of PARS in endothelial and Schwann cells; 4)presence of DNA single-strand breaks after a short (endothelial cells) and prolonged (Schwann cells) exposure to hyperglycemia; 5) evidence of PARS activation in endothelial cells in short-term diabetes and recent demonstration of its key role in diabetes-induced endothelial dysfunction, and 6) applicant's preliminary data demonstrating correction of diabetes-induced motor and sensory nerve conduction velocities (MNCV and SNCV) and energy failure by two specific structurally diverse PARS inhibitors, 3-aminiobenzamide (3-AB) and 1,5-isoquinolinediol (ISO). The EXPERIMENTAL APPROACH will include in vivo evaluation of PARS inhibitors on NBF, conduction, bioenergetics, oxidative stress and nerve growth factor (NGF) abundance in early DN, and on these measures plus nerve morphometry in advanced PDN in the rat model, comparison of PDN in PARS-deficient (+/- or-/-) mice and the wild-type, and the studies of the role of PARS in hyperglycemia-induced apoptosis in vasa nervorum and endothelial cells. The SPECIFIC AIMS are 1) evaluate 3-AB, ISO and PJ34 (a novel potent PARS inhibitor) on NBF, MNCV, SNCV, bioenergetics, oxidative stress and NGF levels in early DN (rats with 6-wk diabetes); 2) evaluate PJ34 on these and morphometric indices in advanced DN (rats with 8-mo diabetes); 3) compare PDN in PARS-deficient (+/- or -/- mice) and the wild-type; and 4) evaluate 3-AB, ISO and PJ34 on hyperglycemia-induced apoptosis in vasa nervorum and endothelial cells. The studies are of direct relevance to the pathogenesis of PDN and may provide the rationale for development of PARS inhibitors for its prevention and treatment.